Comparison of the microbial community structure between inflamed and non‐inflamed sites in patients with ulcerative colitis

<jats:title>Abstract</jats:title><jats:sec><jats:title>Background and Aim</jats:title><jats:p>The gut microbiota is suggested to play an important role in the pathogenesis of ulcerative colitis (UC). However, interindividual and spatial variations hamper the identification of UC‐related changes. We thus investigated paired mucosa‐associated microbiota obtained from both inflamed and non‐inflamed sites of UC patients and corresponding sites of non‐inflammatory bowel disease (IBD) controls.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>Mucosal biopsies of both inflamed and non‐inflamed sites were obtained from 14 patients with active UC of the left‐sided or proctitis type. Paired mucosal biopsies of the corresponding sites were obtained from 14 non‐IBD controls. The microbial community structure was investigated using 16S ribosomal RNA gene sequences, followed by data analysis using <jats:sc>qiime</jats:sc> and LEfSe softwares.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>Microbial alpha diversity in both inflamed and non‐inflamed sites was significantly lower in UC patients compared with non‐IBD controls. There were more microbes of the genus <jats:italic>Cloacibacterium</jats:italic> and the Tissierellaceae family, and there were less microbes of the genus <jats:italic>Neisseria</jats:italic> at the inflamed site when compared with the non‐inflamed site in UC patients. Decreased abundance of the genera <jats:italic>Prevotella</jats:italic>, <jats:italic>Eubacterium</jats:italic>, <jats:italic>Neisseria</jats:italic>, <jats:italic>Leptotrichia</jats:italic>, <jats:italic>Bilophila</jats:italic>, <jats:italic>Desulfovibrio</jats:italic>, and <jats:italic>Butyricimonas</jats:italic> was evident at the inflamed site of UC patients compared with the corresponding site of non‐IBD controls. Among these taxa, the genera <jats:italic>Prevotella</jats:italic> and <jats:italic>Butyricimonas</jats:italic> were also less abundant at the non‐inflamed site of UC patients compared with the corresponding site in non‐IBD controls.</jats:p></jats:sec><jats:sec><jats:title>Conclusions</jats:title><jats:p>Mucosal microbial dysbiosis occurs at both inflamed and non‐inflamed sites in UC patients. The taxa showing altered abundance in UC patients might mediate colonic inflammation.</jats:p></jats:sec>